Edit: I've now decided to keep the tutorial on XDA. I might also keep a copy on the blog, not sure yet

P.S: A lot of this tutorial is based on the original development tutorial which can be found here, credits to rovo89

Tutorial 1 - Setting up

There are a few requirements for making an Xposed Module.
*Eclipse, or Java IDE of your choice, with Android SDK and devlopment enviornment set up. I'm not going to cover that in this tutorial
*Knowledge of Java programming language
*An android phone which supports Xposed, with Xposed installed and working for testing on
*Some knowledge of Android development
*Time
*An idea of course

For the purpose of this tutorial, we will be creating two modules (using two different features of the xposed bridge). The first will replace the clock in the status bar with a smiley face. The second will change the height of the navigation bar. I will be using Eclipse or Android Studio in this tutorial.

At this point you can run the application on your test device. It should show up in the Xposed Installer app as a module. Check the box to enable your module and reboot your device. Of course, the module won't do anything yet!

A good idea at this point would be to add a new filter to your logcat to track error messages from Xposed.

Studio: Go on Android Monitor (along bottom). Make a new filter and filter by tag name. The tag is "xposed"Eclipse:

Add a filter named "Xposed" and filter by the tag name "Xposed"
(picture is for Eclipse)

You will now see messages from the Xposed Framework

There will be an error for your module about xposed_init file, don't worry, getting to that!

Make a new package (same as package name we used when making the Android Project) and within that package make a class. Call it anything, I'll call mine Main.

Secondly add the XposedBridge API jar. This can be found on this thread on XDA. Add the jar to the root directory of the project, NOT the lib directory.Eclipse: Right click - build path - add to build path. Do not export it in the Order and Export tab.

Studio: Right click, add as library. Then go in gradle files and find build.gradle for the app module. Find the dependency which looks something like this
compile files('src/main/java/com/hamzahrmalik/xposedtutorial/XposedBridgeApi-54.jar')
and change the "compile" to "provided" so it is like
provided files('src/main/java/com/hamzahrmalik/xposedtutorial/XposedBridgeApi-54.jar')

Now create a file in the assets directory called xposed_init. Studio users:
First you will need to make the assets directory. I think the easiest way is to first switch to "project files" view at the top of the navigation pane as shown below. Then create a folder inside src/main called assets. Then place the xposed_init in the assets folder.

Inside this file, type:

packagename.classname

where packname is the name of your package and class name is the name of your class. So in my case I will type

com.hamzah.smileyclock.Main

This tells Xposed where to look for the code for the module. You file tree should now look like this

Now the project is set up. In the next tutorial, we will look at how Xposed works, this will help you understand how to make modules.

Tutorial 2 - Brief introduction to how Xposed works

This tutorial is not really a true tutorial (gasp!). It will outline some basic features of Xposed which will help you understand future tutorials.
Xposed allows a developer to access and modify the code for system applications. For example, one useful feature is the "find and hook" feature. This allows a developer to find a method inside another application and add their own code after it. So you could find the method in the Android source code that alerts the user when the wrong pattern is entered, and then instruct the system to hook onto that method and edit the alert to say something else. Another thing that Xposed allows us to do is replace resources. This includes Strings dimensions, drawables and much more. So we could edit the dimension of the navigation bar height (which we will in later tutorials) by replacing the resource which tells it what height to be.

The next tutorial, we will start exploring the Android code and see what methods to hook to replace the clock with a smiley face!

Tutorial 3 - Exploring the target and modifying it

Ok so at this point, you should have an Xposed mod thatdoes nothing. The next step is to work out exactly what we want it to do! We want it to edit the clock, by hooking the method (read the last tutorial for more informtion on this). So the first step is to find that method.

So visit http://grepcode.com/project/reposito...droid/android/ in your browser to view Android's source code. If (in Android 4+) you browse to com.android.systemui.statusbar.policy.Clock.java
you will find the class that controls the clock. In here, there is a handy method called updateClock() which ppears to be controlling what gets written to the TextView in the statusbar (this whole class extends TextView). Now if you know how to make Android apps (which you should) you will be familiar with TextView. We can manipulate this TextView by changing colour, text, font, size etc, as you could with a TextView in a normal Android app.

Of course this was easy, but depending on exactly what you want your module to do, you may have to hook many methods. If you've ever modded APK's, you'll know what i mean ;)

This was another short tutorial, in the next one we will start coding the module

Tutorial 4 - The Code

In this tutorial we can finally get to some code. Exciting right?
OK so we now have the following information
*We can hook methods using Xposed
*There happens to be a method which writes text to the clock
*We can hook this method to edit the text

So first of all, fire up your eclipse workspace and have you Xposed class implement IXposedHookLoadPackage
Then add unimplemented methods.
Your class should now look like:

The method that we are overriding gets called every time the user or system opens an app. We can use the parameter of the method to check when systemui gets loaded, then hook into it and modify the clock. Easy right?

Add this inside your method

Code:

if (!lpparam.packageName.equals("com.android.systemui"))//check if the package being loaded is systemUI
return;
//All code here is only called if it is indeed SystemUI

Explanation: The findAndHookMethod is hooking onto com.android.systemui.statusbar.policy.Clock
The afterHookedMethod allows us to add our own code after the system method is executed, so in this case, the code to add a smiley face will go here. The MethodHookParam allows us to modify the TextView of the method we are hooking. So we need to get hold of that TextView, add this code

Code:

TextView tv = (TextView) param.thisObject;

This is the TextView containing the clock, whatever we do with this TextView at this point, will happen to the TextView in the statusbar, So now simply add

Code:

tv.setText(":)");

This will replace the clock with a smiley face. Alternatively, use

Code:

tv.appendText(":)");

to keep the time and add the smiley after it

Now deploy the app to your test device, and reboot. You should see a smiley face in place of the clock!

That's it for SmileyClock, in the next tutorial, we will look at another feature of Xposed, that is, replacing resources, and will enable/disable the screen wake up on unplug and also edit the height of the system navigation bar.

Tutorial 5 - Replacing Resources

Xposed allows us to replace resources such as String, int, boolean, dimen, or even drawables. In this tutorial we will enable/disable screen wake-up on unplug and in the next one, replace the dimen of navigation bar height and width to make it half size. Simple resources like int and String can be replaced by passing the new value as a parameter but more complex ones like drawable and dimen must be referenced from your own resources. Don't worry, I'll explain it all!

First, we will replace a boolean which tells the system whether or not to wake the screen on unplug. There is a boolean in the framework-res.apk (found in /system/framework) which tells the system this information. We can used Xposed to edit this value, without touching the APK. My phone's default is false so I'm going to make it true, if yours is already true, make it false to make it more noticeable. In a future tutorial, when we learn saving preferences, we will add the ability for the user to set the value. For now, it will be hard coded.

Firstly set up a new project as in tutorial 1. Call it anything. Again, no activity or icon required, though you might want an icon anyway.

Have your class implement IXposedHookZygoteInit

and add unimplemented methods. This is called before anything else and we will use it for replacing our resource.

android is the package name of framework-res, bool is the type of resource (boolean) "config_unplugTurnsOnScreen" is the variable we are replacing and false is the new value.

Now when you run this module, enable and reboot, you should find that if you plug in a charger, turn off the screen, and unplug it, nothing will happen. If you were to change it to TRUE instead of FALSE, when you unplugged, it would wake the screen.

In the text tutorial, we will replace the navigation bar height

Tutorial 6 - Complex Resources

In this tutorial we will change the height of the navigation bar to 36dp, normal is 48dp. Much is the same as last time, but there are a few differences. Once again, set up a new project. Have your module class implement IXposedHookZygoteInit once again. Also implement IXposedHookInitPackageResources
Add the unimplemented methods.

The first 3 parameters are the same as the ones in tutorial 5. The last one has the same function as in the las tutorial, but rather than passing a variable, we are forwarding a resource. This could also be done with drawables, I once made a module to replace all buttons on the navigation bar with the ones found on Xperia ROM's.

At this point, when you deploy the module, enable it and reboot, your navigation bar should be noticeably smaller.

In the next tutorial we will look at creating and user interfaces and saving data in ways that both interface and module can read and write to. We will be using the mod we made in tutorial 4, and allow the user to define text rather than have a smiley face.

Tutorial 7 - User Interfaces and Preferences

Open up the SmileyClock we made in Tutorial 4. We did not make an Activity so make one now, File>New>Android Activity. Make sure you make it a Launcher Activity. We need to widgets in our UI, a textbox and an Apply button. I'm not going to cover making these, just make sure you have a method called when the button is pressed. Make the EditText id "input" so it will be easier to follow the tutorial because that is what i am making mine.

The mode world readable is crucial to allow the Xposed Module to read it, otherwise you will get permission denied. Now get the Editor and save this string as "user_text",

Code:

Editor editor = pref.edit();
editor.putString("user_text", input);

Now it is saved, we need the Xposed Module to read it. Switch back to the class containing the Xposed Module, the one we made in tutorial 4. Find this line:

Code:

tv.setText(":)");

Instead, replace it with this

Code:

XSharedPreferences pref = new XSharedPreferences("com.hamzah.smileyclock", "user_settings");
//Gets the shared preference
String text = pref.getString("user_text", "");
//reads the value which is saves, using nothing as default value to use if nothing is saved
tv.setText(text);
//sets the text to saved value

When you deploy this and set some text, that text should then appear in the status bar after the clock. Note that when you save this value, it will not change in the statusbar until you restart SystemUI. It might change when time changes, not sure.

In the next tutorial we will cover modifying layouts

Tutorial 8 - Modifying Layouts

Xposed lets us modify layouts in other apps. In this tutorial, we will modify the navigation bar with various tweaks. Firstly we will make the background blue. So make a new Xposed Project and have your module class implement IXposedHookInitPackageResources. This gives is a parameter that can be used for modifying layouts. Add the unimplemented method and add this code inside the method

com.android.systemui is the package name for the app containing the navigation bar View, layout is the type of resource, navigation_bar is the View name as defined in /res/layout (of SystemUI.apk). Now we need to get a View object for the navigation bar. Add this code inside the overriden method

When you run this on your phone, your navigation bar will be blue. Now of course you can also call other methods, such as adding in new TextView's or whatever. If you were to inspect the code more closely, you would find there are also ids called "home" "back" and "recent_apps". You could use these to mess around with the buttons, though I cannot imagine what!

Tutorial 9 - Methods with parameters

In an earlier tutorial, we covered hooking methods. But what if a method wants a parameter too?

Say if i want to hook onCreate(Bundle savedInstances) in com.android.settings

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